JP2011175645A - Calibration method and calibration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of calibrating a module which is operated based on a module clock signal. <P>SOLUTION: The method of calibrating the module whose operation is dependent on the module clock signal includes: a step of obtaining over each calibration period of a plurality of such periods, a measure of the frequency of an observed signal, the observed signal being the module clock signal or a clock signal generated based upon the module clock signal; a step of influencing operation of the module in dependence upon the obtained measures to calibrate the module; and a step of taking account of for each calibration period, a position for the end of that calibration period relative to a particular feature of the observed signal and delaying the start of the following calibration period relative to a subsequent particular feature of the observed signal in dependence upon that position. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method and circuit for performing a calibration, for example, a calibration of a module whose operation is based on a module clock signal. Such calibration may be, for example, an ongoing (eg, on-the-fly) calibration when using the module. The module may be, for example, a real time clock (RTC) unit.

  An RTC unit is understood to be a kind of “computer” clock, for example implemented in the form of an integrated circuit and generally used in relatively large circuits or systems such as microcontrollers. I can do it. Such computer clocks are typically used to track the current time and can track, for example, time and date. Thus, RTC units are available in almost all electronic devices that need to maintain “accurate” time (which may be part of a relatively large one such as an automobile or industrial robot).

  Many electronic devices have a strong demand for low power consumption. Such a requirement can be met by a low power operating mode in which a fast and accurate reference clock signal is switched off. In such a low power mode, the embedded RTC unit or another similar module is a second relatively slow and usually relatively inaccurate clock signal ("module clock signal"). The operation can be maintained in a clocked state. The use of a relatively slow clock signal can result in a relatively low power consumption compared to the use of a relatively fast clock signal. A clock source for such a module clock signal, and generally less accurate than that of the reference clock signal, will be susceptible to large temperature drifts, weather, and aging. These factors can adversely affect the accuracy of the RTC unit.

  A method for calibrating the RTC unit has already been studied. In general, such already discussed methods can be classified into two categories, but there will be some overlap in these categories.

  In the first category, the time value itself of the RTC unit can be corrected. This category of methods generally measures the frequency error of the RTC unit clock signal (module clock signal), for example, at fixed intervals or in response to temperature changes.

  Such measured values tend to be collected in relation to a reference clock signal that is more accurate than the module clock signal.

  Based on the measured error and the elapsed time from the last correction cycle, the deviation time amount of the time value of the RTC unit is calculated. The deviation may be positive (which indicates that the module clock signal is too slow) or negative (which indicates that the module clock signal is too fast). After this, the time value of the RTC unit itself (which may be hours, minutes, seconds, milliseconds as appropriate) can be corrected, or the time value of the RTC unit can be returned to the correct value. It is also possible to temporarily replace the module clock signal of the RTC unit with a faster or slower clock signal.

  A disadvantage of the first category of methods would be a discontinuity or sudden speed change in the time value of the RTC unit (eg, a “jump” of the time value) caused by the correction operation described above.

  The disclosure of this category includes Patent Document 1, Patent Document 2, and Patent Document 3.

  In the second category, it is possible to influence the operation (or module clock signal) of the RTC unit itself to perform correction.

  As in the first category, in general, the module clock signal of the RTC unit can be measured in some way, for example to find its frequency. As described above, a more accurate reference clock signal can be used. Calibration can be triggered only once in a fixed time interval based on the measured temperature change or once during the manufacture of the relevant device. The measured frequency value can then be processed in hardware or software to determine the calibration required for the RTC unit.

  In this category of methods, several different delay lines (special integrated circuits) can be used to directly trim the clock oscillator of the RTC unit, and thus the RTC clock can be corrected directly. These methods provide high accuracy, but will impose strict requirements on the manufacturing quality of the delay line and its stability over time and temperature.

  It is also possible to perform temperature dependent oscillator trimming with correction values derived from known temperature profiles. Due to the slow temperature change (in the normal case) and the appropriate periodic calibration interval, such a method will not show a large discontinuity in the time value of the RTC unit. However, such a method has the problem that the achievable accuracy is limited depending on the fixed step size of the calibration value (eg oscillator trimming value), which usually results in time A minimum residual error that accumulates over time is generated. In such a case, it may be necessary to implement further averaging in software, for example, in order to reduce error accumulation.

  The disclosure of this category includes Patent Document 4, Patent Document 5, and Patent Document 6.

US Patent Application No. 2008/0082279 (US-A1-2008 / 0082279) Specification Chinese Patent Application No. 1622045 (CN-A-1622045) Specification US Pat. No. 6,304,517 (US-B1-6304517) specification International Patent Application Publication No. 2005/088424 (WO-A2-2005 / 088424) Pamphlet International Patent Application No. 97/04366 (WO-A1-97 / 04366) Pamphlet US Patent Application No. 2008/0222440 (US-A1-2008 / 0222440) Specification

  It would be desirable to improve the calibration method of existing modules (eg, RTC units). For example, it is desirable for the RTC unit to have high accuracy over a long operating period while utilizing the clock source of the low accuracy RTC unit. It is also desirable for the RTC unit to be automatically calibrated in response to changes in unit clock frequency without requiring additional sensor hardware. It should be understood that the RTC unit is only an example of a module to which the present invention can be applied.

  According to a first aspect of the present invention, a method is provided for calibrating a module whose operation is based on a module clock signal, the method comprising: observing a signal to be observed in each calibration period of the plurality of calibration periods. Obtaining a frequency measurement, wherein the signal to be observed is a module clock signal or a clock signal generated (optionally by the module) based on the module clock signal, and calibrating the module Therefore, considering the time position of the end point of the calibration period in relation to the specific characteristics of the observation target signal for each of the aforementioned calibration periods and the step of affecting the operation of the module based on the acquired measurement values And the subsequent signal in relation to the specific feature of the subsequent observation signal based on its position. After) having, delaying the starting point of the calibration period.

  Such a module may be, for example, a real-time clock unit, which may be part of a larger device such as a microcomputer.

  The calibration periods preferably have the same duration as each other, but in some embodiments (configurable to perform complex calculations), the calibration periods can have different durations.

  The intervals between calibration periods preferably have substantially the same duration as each other, but in some embodiments (configurable to perform complex calculations), the intervals between calibration periods Each can have a different duration.

  The operation of the module is preferably influenced by the measurement values obtained from one calibration period until the next calibration period, during which the newly obtained measurement value is obtained at that time. Is used. Optionally, a combination of measured values obtained (for example, a mathematical operation such as averaging applied) can be used to influence the operation of the module. Optionally, any obtained measurement can be used to influence the operation of the module.

  The method comprises, for each such calibration period, arranging the calibration period in time such that the starting point of the calibration period is delayed in relation to the specific characteristic of the observation signal. It is possible that the delay is equal to the period between the end point of the preceding calibration period and the particular characteristic of the observed signal preceding that end point.

  The method is such that, if the portions of time are concatenated to eliminate that or each full clock cycle of the signal under observation during the calibration period, the successive calibration periods are continuous in time. It is possible to have a step of arranging the calibration periods in time.

  The duration of each calibration period can be determined in relation to a time signal that is more accurate than the signal to be observed. Such a time signal may be, for example, a reference clock signal. The reference clock signal can have a clock frequency that is higher (eg, significantly higher) than that of the module clock signal or the signal to be observed.

  The duration of each calibration period can be determined by counting a predetermined number of features of the reference clock signal. For example, the rising and / or falling edges of the reference clock signal can be counted.

  The method may comprise operating the circuit in a low power mode where the circuit does not utilize a reference clock signal during such successive calibration periods. For example, the circuit can be operated in such a low power mode during successive calibration cycles. The circuit can be operated in such a low power mode in periods other than the calibration periods and the delays (delay periods) applied during those periods. The method can include disabling the reference clock signal so that the reference clock signal is not valid when the circuit is in a low power mode.

  Calibration periods (or calibration cycles with those calibration periods) can be implemented periodically. This regularity can be determined in relation to the signal of the module (such as a time signal) that benefits from the calibration described above.

  The method measures the delay period between the end point of one calibration period and the aforementioned particular feature of the preceding observation signal, and the start point is related to the aforementioned particular feature of the subsequent observation signal. It is possible to have the step of arranging the calibration period in time by starting the next calibration period so as to be delayed in, the delay being equal to the measured delay period. Each delay period can be measured by counting the characteristics of the reference clock signal.

  The calibration periods can have the same duration as each other.

  The method can comprise obtaining the aforementioned measured value of the frequency of the observation target signal by counting the characteristics of the observation target signal for each calibration period.

  The step of imparting influence may comprise setting a time reference utilized by the module. The step of influencing may comprise the step of influencing the operation of the module based on the measured values obtained for each calibration period following each calibration period. That is, until the next measurement value is obtained, each obtained measurement value can be used in the step of giving such an effect, and so on. Each obtained measurement value can be directly used as a time reference value set in the module.

  The characteristics of the various signals that are being counted or monitored may be rising and / or falling edges.

  The method can be performed in hardware, for example, by performing such a counting step using a counter. The module may be a real time clock unit.

  Disclosed herein is a method of calibrating a module whose operation is based on a module clock signal, the method comprising comparing an observed signal with a time signal, wherein the observed signal is: Module clock signal or a clock signal generated by the module based on the module clock signal, and the time signal is more accurate than the signal under observation, and the module based on the result of such comparison Adjusting the time base utilized.

  Disclosed herein is a method for calibrating a module whose operation is based on a module clock signal, wherein the method characterizes an observed signal in each calibration period of the plurality of calibration periods. And the observation signal is a module clock signal or a clock signal generated by the module based on the module clock signal, and following each calibration period, the result of the related counting step On the basis of configuring the operation of the module.

  According to a second aspect of the present invention there is provided a microcontroller configured to perform the aforementioned method, for example according to the aforementioned first aspect of the present invention.

  According to a third aspect of the present invention, there is provided a circuit configured to perform the aforementioned method, for example, according to the aforementioned first aspect of the present invention. Such a circuit can have the aforementioned modules.

  Embodiments of the present invention can be used in the form of microcontrollers in mobile communication devices such as mobile terminals, base stations, and relay stations, in automobiles, or in industrial robots, for example.

  Reference will now be made, by way of example only, to the accompanying drawings described in the section "Brief description of the drawings".

1 is a circuit diagram of a circuit using the present invention. 2 is a flowchart of a method utilizing the present invention. 1 is a circuit diagram of a system using the present invention. FIG. 4 is a timing diagram useful for understanding the principles utilized by the embodiment of FIG. FIG. 5 is a timing diagram similar to FIG. 4 but showing breaks or gaps between successive calibration periods, where the gaps represent periods of low power operation. FIG. 4 is a circuit diagram of an exemplary implementation of the automatic calibration unit of FIG. 3. 2 is a flowchart of a method utilizing the present invention.

  FIG. 1 is a circuit diagram of a circuit 1 embodying the present invention. The circuit 1 has a module 2 and calibration means 4.

  The module 2 is configured to operate based on the input module clock signal (MCS). In the exemplary circuit 1, the module 2 is configured to output a module output signal (MOS) based on the input MCS. Accordingly, the MOS can be considered to be generated from the MCS or generated based on the MCS, and may be a version obtained by dividing MCS by 2, for example. Module 2 can also output another signal (not shown) that is affected (ie, calibrated) by calibration as described below.

  The calibration means 4 is configured to obtain a measurement value of the frequency of a signal generated from an MCS or an MCS such as a MOS in each of the calibration periods. The MCS and MOS inputs to the calibration means 4 are represented by dashed lines in FIG. 1 to show that in some embodiments only one is available. In one embodiment, the measured value of the frequency of MCS may be a result of counting features of MCS or MOS (observation target signal (OS)).

  The calibration means 4 is based on an accurate time signal generated internally, or based on an accurate time signal supplied from the outside shown in FIG. 1 such as a reference clock signal (RCS), for example. It can be configured to control the duration of each calibration period. The input of the RCS in FIG. 1 is again represented by a dashed line to indicate that it may be optional (in the sense that an internally generated accurate time signal is available). Yes.

  An RCS or other time signal utilized by the calibration means 4 can be considered “accurate” in the sense that it is more accurate than MCS. In one embodiment, the RCS or other time signal utilized by the calibration means 4 can be considered “accurate” in the sense that it is complete.

  The calibration means 4 can determine the calibration period (or calibration period and the delay applied to the calibration period) based on MCS or MOS or RCS or another signal or based on a combination of such signals. It is possible to determine when to perform a calibration cycle). Module 2 can also determine when to perform a calibration period (or calibration cycle) based on these available signals. In practice, for example, by using such signals, it is possible to determine when to perform a calibration period (or calibration cycle) utilizing external hardware or software.

  In one embodiment, the calibration means 4 can count, for example, the rising or falling edge or the length of the period as a feature of the OS. In general, it should be understood that features of any signal can be counted.

  Following each calibration period (or calibration cycle), the calibration means 4 outputs a calibration signal CS to the module 2 to influence or configure the operation of the module 2, so that the module It is operable to calibrate the operation. The calibration means 4 generates CS based on, for example, related measurement values acquired in the preceding calibration period or by considering a plurality of preceding calibration periods. The acquired measurement value may be the result of the counting step as described above. As will become apparent, such an influencing or calibration step functions to compensate for inaccuracies in the observed signal in relation to the reference clock signal.

  The step of influencing may include adjusting or setting a time reference utilized by module 2, eg, setting or adjusting the capacitance of a capacitor utilized by the module, or controlling a delay line utilized by the module. It may involve a step to perform. In a preferred embodiment, the step of influencing involves adjusting or setting a time reference.

  The calibration means 4 determines that the length of the time interval between successive calibration periods is substantially an integer number of clock cycles of the OS (ie one or more total clock cycles). The calibration period is arranged in terms of time in relation to It should be understood that such time intervals need not start or end with the rising or falling edge of the OS.

  In other words, the calibration means 4 connects the respective parts of time so that successive calibration periods are separated in time by at least one or more intermediate full clock cycles of the OS, and each or each When the above intermediate full clock cycles are eliminated (these cycles do not necessarily have to start or end with a rising or falling edge), the aforementioned consecutive calibration periods have the same temporal relationship with each other. As described above, the calibration period is arranged in terms of time in relation to the OS. Such a temporal relationship may be such that successive calibration periods are substantially adjacent, continuous, or touching after connection.

  The calibration means 4 can use RCS and OS (MCS, or MOS, or another signal based on MCS) to arrange the calibration period in time. For example, the calibration means 4 may utilize an OS such that successive calibration periods are separated in time by at least one or more intermediate full clock cycles of the OS. For example, the calibration means 4 can count the full clock cycle of the OS. The calibration means 4 uses, for example, RCS to measure the period between the last feature of the OS in one calibration period (eg rising edge) and the end of the calibration period, and then the period is By applying RCS and OS (such as using RCS) as a delay in relation to subsequent OS features (eg, rising edge) before starting the calibration period, such temporal composition Can exist.

  The combination of applied delay and subsequent calibration period can be referred to as a calibration cycle.

  It should be understood that the calibration cycle can be triggered externally if, for example, multiple MCSs (not shown) are provided and switching between the MCSs is desired. For example, the calibration cycle can be triggered manually or by external software or hardware.

  FIG. 2 is a flowchart defining a method 6 for implementing the present invention. Method 6 has step 8, step 10, step 12, step 14, and step 16.

  In step 8, it is determined whether to start a new calibration period. Therefore, method 6 effectively waits until the start of a new calibration period (“No” in step 8). If a new calibration period is to be started (“Yes” in step 8), the method proceeds to step 10.

  It should be understood that the delay is applied based on the location of the end point of the previous calibration period before the new calibration period actually begins. As mentioned above, the applied delay and the subsequent calibration period can be collectively referred to as a calibration cycle.

  In step 10 where the relevant calibration period is believed to have actually begun, OS features are counted as an example of a technique for obtaining a measurement of the frequency of the OS. In step 12, it is determined whether the current calibration period has expired. Therefore, Method 6 effectively waits until the end of the calibration period by continuing such a counting step in Step 10 (“No” in Step 12). If the calibration period has expired (“Yes” in step 12), the method proceeds to step 14. Record the position of the end point of the calibration period to determine the delay to apply for the next calibration period.

  In step 14, an influence is given to or configured on the operation of the module 2 based on the acquired measurement value. In this example, the acquired measurement value is a result of the count step in step 10. is there. The method then proceeds to step 16.

  In step 16, it is determined whether to wait for a further calibration period (or further configuration cycle), i.e. whether there is a further calibration period. If there is no further calibration period, for example if it is determined that no further calibration period is required for any reason, the method ends (“No” in step 16). Otherwise, the method returns to step 8 (“Yes” in step 16) and waits for the correct time to start the next calibration cycle.

  As will become apparent, the subsequent examples disclosed herein relate to RTC units, but the present invention may be any unit that requires maintenance of accurate time tracking, for example, Or, for example, any other unit whose operation is based on a module clock signal, such as any device that needs to operate in synchronization with one clock signal but does not always use that clock signal. It also applies to (module) calibration.

  Hereinafter, an outline of an embodiment for automatic calibration of the RTC unit will be described. In this embodiment, the reload value of the time base counter of the RTC unit (operating on the basis of the RTC unit clock signal or MCS) is set so that the time value of the RTC unit follows the correct time value as closely as possible. It is adjusted periodically or sometimes. A relatively high accuracy reference clock signal (RCS) is used, and a relatively low accuracy RTC unit clock signal (MCS) is measured. As will be described in more detail below, for a specific period (measurement window or “calibration period”), two counters (in relation to the rising edge of MCS) and the MCS full cycle (at the end of the measurement window) by two counters The MCS period residual value (in relation to the rising edge) is measured respectively.

  In the disclosed embodiment, the full cycle value (which may be the number of rising edges counted) is directly used as the reload value for the time base counter of the RTC unit. Can be used indirectly in relation to another value, for example. For example, it can be used as part of a numerical operation (eg, multiplying by a factor to match a desired time reference). Such time base counters are typically utilized to convert clock cycles into useful units of time such as seconds, minutes, and hours. For example, the greater the reload value of the time reference counter, the greater the number of clock cycles that need to be counted, for example, to measure the time of one second.

  In the following embodiments, the period remaining value at the end point of the measurement window (calibration period) is used, and the start point of the next measurement window (calibration period) is delayed in relation to the rising edge of MCS. As a result, as will become apparent, a modulation of the reload value is achieved that causes the reload value to closely follow the optimum value (this value varies with time to compensate for inaccuracies in the module clock signal). By utilizing the embodiments (circuits, methods, etc.) disclosed below in an electronic circuit, the RCS calibration cycle (each cycle is the delay applied to the start of the calibration period and its calibration period) High accuracy and automatic recalibration of the RTC unit in response to MCS inaccuracies (e.g. due to temperature drift) while enabling low power operation It is feasible.

  The embodiments disclosed below are preferably configured to operate without further interaction with the execution code of a microcontroller (as an example of an electronic device). That is, this embodiment provides for autonomous execution of calibration without the need for interaction with another entity (eg, computation by such a microcontroller). This embodiment is, of course, generally applicable to embedded units (such as RTC units) and electronic devices with dual-clock operating capability, where the microcontroller is one example type. is there.

  As described above, the RTC unit can generate its time reference (eg, 1 second duration) with a reload counter that is clocked by the RTC module clock signal. The reload value determines the length of the time base. By adjusting this reload value, the RTC time base can be calibrated. Due to adjusting the reload value only in increments of full clock cycles (fractional values are discarded), the accuracy of the system will be limited. Depending on the RTC clock frequency and the length of the time reference, residual errors can quickly accumulate and deviate by a few minutes per month. However, embodiments of the present invention (e.g., subsequent embodiments) address this potential problem and produce a reload value modulation (as will become apparent). As a result, the resulting reload value can generally have a tendency to closely follow the ideal value.

  A further challenge in the RTC calibration system is to detect and recalibrate the frequency drift of the RTC clock caused by external influences (eg, temperature, humidity, etc.). For example, embodiments of the present invention, such as subsequent embodiments, automatically correct for external influences such as temperature drift (which occurs at a relatively slow rate). The accuracy of the RTC time reference that can be achieved in relation to temperature drift will depend substantially only on the quality of the reference clock signal and the calibration interval. For example, there is no need for additional temperature sensors.

  As will become apparent, the subsequent embodiments show that high accuracy that is feasible, automatic calibration to compensate for frequency drift, no need for additional sensors (such as temperature sensors), and low mounting loads (eg, Is considered advantageous because no additional mathematical processing is required).

  FIG. 3 is a circuit diagram of a system 100 that implements the present invention. The system 100 includes an RTC unit 120, a system oscillation unit (SOU) 140, and an automatic calibration unit (ACU) 150. System 100 is operable to receive an RTC clock signal (MCS) 110 and a system clock signal (RCS) 130.

  As shown in FIG. 3, the ACU 150 is built into the system 100. The RTC clock signal 110 (A) is input to the RTC unit 120 as a clock supply source. The RTC unit 120 is configured to generate / control its time reference by a reload timer (not shown) configured to count under the control of the RTC clock signal 110 (A). Therefore, the reload value of the reload timer sets the RTC time base duration. As shown in FIG. 3, this reload value can be set or controlled by a signal (F) supplied by the ACU 150.

  System clock signal 130 (B) is provided to SOU 140, which in this embodiment is faster and more accurate than RTC clock signal 110 (A). The SOU 140 is configured to supply the derived reference clock signal (E) to the ACU 150 based on the system clock signal 130 (B). Accordingly, the reference clock signal (E) can be considered to be the same as or dependent on the system clock signal 130. The SOU 140 is operable to switch on / off the system clock signal (B) and / or its derived reference clock (E).

  The ACU 150 is configured to be clocked by the supplied reference clock signal (E). Also, as will become apparent, an RTC clock signal (A) is also input to the ACU 150 for use in performing calibration and / or generating a wake-up / sleep signal (D).

  After a calibration cycle (applied delay plus calibration period), a time reference reload value signal (F) is input to the RTC unit 120 and switches off the oscillation of the reference clock signal (E). Therefore, the sleep signal (D) is output to the system oscillation unit 140. It should be understood that the time base reload value signal (F) can maintain or change the current time base reload value.

  The RTC unit 120 is used in determining the duration of the interval between successive calibration cycles, i.e., for generating a calibration interval, the tick signal (C) to the ACU 150. Is configured to supply. The tick signal (C) may be based on the received rising edge of the RTC clock signal (A) modulated by the (calibrated) time reference of the RTC unit 120, as an example. When the calibration interval elapses, this signals that a new calibration cycle will begin, so that the main oscillating unit (SOU 140) will switch on the oscillation of the system clock signal (B) and the reference clock signal (E). Wake up (D) and a new calibration cycle is started. The SOU 140 turns on and off the reference clock signal (E) and the system clock signal (B) simultaneously under the control of the wakeup / sleep signal (D), for example, to save power when both are off, It should be understood that it may be operable.

  Before describing the system 100 in more detail, first the theory of operation will be described.

The system 100 is configured to automatically determine the (reload) value of the time reference counter of the RTC unit 120 based on the respective calibration period. This time reference counter is configured to count the cycles of the RTC clock signal 110 (A), which can be considered as having a frequency f _RTC . The number of cycles before the counter is restarted defines the time base (time_base), ie, what the module considers to be its minimum time unit duration (eg, 1 second).

The optimum time base reload value (reload_value _opt ) can be expressed as follows.

reload_value _opt = f _RTC · time_base

  The resulting optimal reload value may typically be a floating point number with an integer and a decimal value. In practice, however, the time base counter can only count full clock cycles, i.e. the fractional part of the RTC clock cycle is not taken into account.

  Depending on the quotient divided by the RTC clock period in the time base, the fractional value will be in the range of 0-1. As with time reference counters, when this decimal value is ignored, each timer tick of the RTC unit will be accompanied by a small error, such error accumulates with time, and the time signal Increase the deviation. For example, it may appear that the RTC unit is operating at an excessively high speed.

  In this embodiment, such deviation can be prevented or compensated by modulating the reload value of the time reference counter. Such modulation is automatically provided in this embodiment by an ACU 150 configured to operate according to the following principles. Please refer to FIG. 4, which is a timing diagram useful for understanding this principle.

  The timing diagram of FIG. 4 shows a continuous calibration cycle with each individual calibration period (measurement window) shown as a series of equal width rectangles indicating that the calibration periods have the same duration as each other. Yes. The RTC clock signal (A) is also shown side by side in the calibration period, and the rising edge of each signal is represented by an arrow pointing downward.

  In the case of FIG. 4 (as opposed to FIG. 5 described below), there are no gaps or breaks between successive calibration periods.

  Within the calibration period, full RTC clock cycles in relation to the rising edge, ie rising edge events, are counted. As shown by way of example in FIG. 4, there are four edges in the first calibration period, three edges in the second calibration period, and four edges in the third calibration period. The same applies hereinafter.

  These calibration periods are generated based on the reference clock signal (E) and are therefore more accurate than the RTC clock signal (A), but are out of sync with it. In theory, as shown in FIG. 4, if one calibration period follows the previous one without a gap, the continuous starting point of the calibration period is the RTC clock. Shift in relation to signal (A). Depending on this changing relative position of the starting point of the calibration period in relation to the RTC clock signal (A), one edge event is counted accordingly. This variation in the counted value directly represents the required modulation of the reload value (controlled by the time reference reload value signal (F)) of the RTC time reference counter. It should be understood that the time reference reload value signal (F) can hold the result of the counting step itself or, for example, an up / down increment signal.

In the case of a stable RTC clock signal (A), the sequence of count results (which can be used directly as a reload value) exhibits a periodic behavior that can be referred to as a repetitive calibration pattern. This calibration pattern is a repeating pattern of 4, 4, 3 in FIG. The average of the values within one period (3.667 in the example of FIG. 4) will be very close to the optimal time reference value (reload_value _opt ). Therefore, the realizable accuracy is now limited only to the accuracy and resolution of the reference clock signal (E).

  It is desirable to have a gap between successive calibration cycles so that the system clock signal (B) can be switched off from time to time to save power. In this regard, see a timing diagram similar to that of FIG. 4, but showing a break or gap between successive calibration cycles (which may correspond to multiple cycles of the RTC clock signal). I want to be. As an example, in one embodiment, the calibration period (of the calibration cycle) can have a duration of 250 ms, and the interval between successive calibration cycles is 1 minute, or in some cases 10 It can have a duration of minutes.

  In order to maintain the behavior of FIG. 4 which shifts the starting point of successive new calibration periods, in this embodiment, the ACU 150 causes the last rising edge of the RTC clock signal (A) within the calibration period and the end of the calibration period to be The remaining time (remaining period) is measured. This “remaining period” represents the desired delay to be applied in the next calibration cycle, ie to delay the start of the next calibration period in relation to the subsequent rising edge of the RTC clock signal ( See FIG. 5). By utilizing this procedure, the system clock signal (B) and / or the reference clock signal (E) are switched during the calibration cycle while maintaining substantially the same behavior as shown in FIG. It is possible to insert a time gap (calibration interval) that is turned off.

  FIG. 6 is a circuit diagram illustrating an exemplary implementation of ACU 150. The ACU 150 includes a calibration interval generator 210, an edge detector 220, a measurement window generator 230, a CNRTTC counter 240, and a CNTDRC counter 250.

  The ACU 150 is configured to operate based on the reference clock signal (E), the RTC clock signal (A), and the tick signal (C), but for the sake of clarity, FIG. The input of the clock signal (E) is not shown.

  The start of the calibration cycle is triggered by the calibration interval generator 210, which is configured to count RTC timer ticks based on the tick signal (C) supplied from the RTC unit 120. When this counter expires, a wake-up signal (D) is output to the SOU 140 to switch on the system clock signal (B) and thus the reference clock signal (E). This will start a new calibration cycle.

  The start of the calibration cycle is synchronized with the RTC clock signal (A). For this purpose, the edge detector 220 supplies a start signal (H) at the next rising edge of the RTC clock. This start signal (H) activates the measurement window generator 230. The measurement window generator 230 starts counting down the delay counter value (I), which is supplied from the CNTDRC counter 250 based on the previous calibration cycle. As the delay value reaches 0, the RTC clock cycle counter (CNTRTC counter 240) is set to 0 (based on a reset signal not shown in FIG. 6) and the calibration of the current calibration cycle The period starts.

  As long as the calibration period (measurement window) is valid, the enable signal (J) is also valid. As long as the enable signal (J) is valid, the RTC clock cycle counter (CNTRTC counter 240) counts up with each new edge strobe signal (K) supplied by the edge detector 220. At the same time, as long as the enable signal (J) is valid, the remaining period CNTDRC counter 250 counts up with each reference clock signal (F) cycle. At each rising edge of the RTC clock signal (A), the edge detector 220 outputs a reset signal (L) and clears the “remaining period” counter CNTDRC 250.

  At the expiration of the calibration period time measured by the measurement window generator 230 with reference to the reference clock signal (E), the enable signal (J) is disabled, so that the counters CNRTTC 240 and CNTDRC 250 stop operating. And each value is held. The reset signal (L) does not clear the “remaining period” counter CNTDRC 250 at this time.

  The counter value of CNTRTC 240 that basically counted edges such as the rising edge of the RTC clock signal in the calibration period (measurement window) of the calibration cycle is the time reference reload value of the RTC unit 120, and in this embodiment, Directly used as a time reference reload value signal (F). The period remaining counter CNTDRC 250 holds the value, which is used as the delay value (I) for the next calibration cycle.

  The measurement window generator 230 then outputs an end signal (M) to the calibration interval generator 210, resulting in a sleep signal (D) being output to the SOU 140. Correspondingly, the system clock signal (B) and the reference clock signal (E) are switched off. The calibration interval generator 210 is restarted to count the timer ticks (C) of the RTC unit until the interval expires and a new calibration cycle is initiated.

  FIG. 7 is a flowchart of a method 300 for implementing the present invention. The method 300 includes steps 302 to 328.

  Method 300 begins at step 302 following the end of a previous calibration cycle. In step 302, the system clock signal (B) and the reference clock signal (E) are switched off to save power between calibration cycles. Then, in step 304, the counter of the calibration interval generator 210 is read so that the interval between calibration cycles can be determined.

  In step 306, when the tick signal (C) is received from the RTC unit 120, the value read into the counter of the calibration interval generator 201 is decremented, at which point the method proceeds to step 308. Proceed to In step 308, it is determined whether the calibration interval has elapsed, that is, whether the value read into the counter of the calibration interval generator 210 has been decremented to zero.

  Method 300 returns to step 306 and when the value read into the counter of calibration interval generator 210 is decremented to zero by decrementing the read value in the next tick signal (C). In effect, the system waits (“NO” in step 308). If the value is decremented to zero (“Yes” in step 308), the method proceeds to step 310 as a new calibration cycle is initiated.

  In step 310, the system clock signal (B) and the reference clock signal (E) are switched on. The method then proceeds to step 312 and waits for the rising edge of the RTC clock signal (A) (as an example clock signal feature) (“No” in step 312). If such a rising edge is detected (“Yes” in step 312), the method proceeds to step 314.

  In step 314, it is determined whether the counter value CNTDRC is equal to 0, and if not equal (“No” in step 314), by continuously passing through step 316, until the time when it becomes equal to 0 (“Yes” in step 314), the value is decremented every cycle of the reference clock signal (E). As a result, the starting point of the calibration period (measurement window) of the calibration cycle is delayed in relation to the rising edge of the RTC clock signal (A) according to the counter value CNTDRC held from the preceding calibration cycle.

  If the counter value CNTDRC reaches 0 (“Yes” in step 314), the method proceeds to step 318, which symbolizes the start of the calibration period of the calibration cycle. In step 318, the counter value CNRTTC is set to zero.

  The method then detects the next rising edge of the RTC clock signal (A) under the assumption that the calibration period (measurement window or measurement time) has not expired (“No” in steps 322 and 324). The loop through step 320, step 322, and step 324 is cycled to the point in time. In each of these loops, the counter value CNTDRC is incremented by 1 at step 320 for each cycle of the reference clock signal (E).

  If a rising edge of the RTC clock signal (A) is detected (“Yes” in step 322), the method passes between steps 322 and 324 via step 326, in which the counter value CNRTTC And the counter value CNTDRC is reset to 0 so that the recorded delay (remaining period) value is formally zero.

  Accordingly, when it is determined that the measurement time (calibration period) has elapsed (“Yes” in step 324), the counter value CNRTTC is the number of rising edges of the RTC clock signal (A) detected during the calibration period. And the counter value CNTDRC represents the “remaining period” time in the clock cycle of the reference clock signal (E), which is the time between the last rising edge of the RTC clock signal (A) and the end of the calibration period. Represents.

  The counter value CNRTTC is then used to set the time reference used by the RTC unit 120. The method then returns to step 302 where the system clock signal (B) and / or the reference clock signal (E) are switched off to put the system into a low power mode of operation. The counter value CNTDRC is held (in steps 314 and 316) to be used as a delay to delay the next calibration period relative to the rising edge of the RTC clock signal (A).

  Appendix 1: This specification includes an RTC unit (120) that operates based on the RTC clock (A) and counts time and date, or any similar unit, and a second clock ( A real-time clock auto-calibration system for an electronic device is disclosed having an auto-calibration unit (150) operating on the basis of a reference clock, E).

  Appendix 2: This specification includes RTC clock signal input (A), reference clock clock input (E), time tick signal signal input from RTC unit (C), and RTC unit time reference reload value Input and output of value output (time reference reload value, F) and wake-up and sleep signal output (D) to control system oscillation unit to switch system clock on and off to provide power saving mode An automatic calibration unit is disclosed that operates in the aforementioned system (see Appendix 1) having

  APPENDIX 3: The automatic calibration unit described above (see Appendix 2) includes a calibration interval and control signal generation unit (210), an RTC clock edge detection and control signal generation unit (220), a measurement window and control. A unit (230) that generates a signal, a unit (CNTRTC, 240) that counts RTC clock cycles, and a unit (CNTDRC, 250) that counts reference clock cycles can be included.

  Appendix 4: This specification includes the steps of counting RTC time tick events to generate a calibration interval, generating a wake-up signal when the calibration interval has passed, and upon entering an end signal (M) Resuming the calibration interval and outputting a sleep signal, and a method for generating a time interval for periodically initiating RTC autocalibration performed by the aforementioned system (see Appendix 3) having Has been.

  Supplementary Note 5: In this specification, the step of detecting the rising edge of the RTC clock, the step of starting the counting of the delay time given by the previous counter value of CNTDRC, and the counter value of CNTRTC when the delay time expires are described. Resetting; starting counting the measurement window time when the measurement window time is running; counting the RTC clock cycle by the counter CNTDRC; counting the system clock cycle by the counter CNTDRC; Resetting the CNTDRC value to 0 at each rising edge of the RTC clock, stopping and holding the counters CNRTTC and CNTDRC when the measurement window time expires, CNT Operating on the aforementioned system (see Appendix 3) having the steps of outputting a TC counter value, outputting an end signal, and using the CNTRTC counter value as the RTC time base reload value An RTC automatic calibration method is disclosed.

  Appendix 6: This specification includes the steps of initiating the RTC autocalibration run described above (see Appendix 5) upon expiration of the calibration interval described above (see Appendix 5) and the termination described above. On output of a signal (see Appendix 5), on the aforementioned system (see Appendix 3), the step of starting the above calibration interval run (see Appendix 4). A method for performing an operating RTC autocalibration routine is disclosed.

  Appendix 7: This specification uses the steps of periodically repeating the method of Appendix 6 above, and using equidistant calibration intervals, so that the behavior of the RTC time reference value over time A method for performing an RTC automatic routine cycle operating on the aforementioned system (see Appendix 3) having the steps of:

  These systems / methods can be implemented in hardware or software. It is desirable to implement these systems and methods in hardware.

  In any of the foregoing aspects, the various features can be implemented in hardware or as software modules running on one or more processors. The features of one aspect are applicable to any of the other aspects.

  The present invention also provides a computer program or computer program product that performs any of the methods described herein and any one of the methods described herein. And a computer readable medium having a program stored thereon stored thereon.

  A computer program that implements the present invention can be stored on a computer-readable medium, or can be in the form of a signal, such as a downloadable data signal provided from an Internet website, or It would be possible to have other forms.

100 system 110 RTC clock signal 120 RTC unit 130 system clock signal 140 system oscillation unit 150 automatic calibration unit

Claims (14)

A method of calibrating a module whose operation is based on a module clock signal,
Obtaining a measurement value of the frequency of the observation target signal in each of the calibration periods of the plurality of calibration periods, wherein the observation target signal is generated based on the module clock signal or the module clock signal A step that is a clock signal;
Influencing the operation of the module based on the acquired measurements to calibrate the module;
For each calibration period, the temporal position of the end of the calibration period is considered in relation to the specific characteristic of the observation target signal, and the specific characteristic of the subsequent observation target signal is based on the position. Delaying the starting point of the subsequent calibration period in relation to
Having a method.   For each said calibration period, arranging said calibration period in time so that said starting point of said calibration period is delayed in relation to said particular characteristic of said observation target signal, The method of claim 1, wherein the delay is equal to a period between an end point of a preceding calibration period and the particular feature of the observed signal preceding the end point.   The method according to claim 1 or 2, wherein the duration of each calibration period is determined in relation to a time signal that is more accurate than the signal to be observed.   The method of claim 3, wherein the time signal is a reference clock signal.   5. The method of claim 4, wherein the reference clock signal comprises a higher clock frequency than that of the module clock signal or the signal to be observed.   6. A method according to claim 4 or 5, wherein the duration of each calibration period is determined by counting a predetermined number of features of the reference clock signal.   7. A method according to any one of claims 4 to 6, comprising operating the circuit in a low power mode in which the circuit does not utilize the reference clock signal during the continuous calibration period.   The method according to claim 1, further comprising the step of periodically implementing the calibration period. Measuring a delay period between one end point of the calibration period and the particular characteristic of the observation target signal preceding the end point;
Starting a next calibration period such that its starting point is delayed in relation to the particular characteristic of the subsequent observation signal, the delay being equal to the measured delay period; Steps,
The method according to claim 1, further comprising the step of arranging the calibration period in time. The time signal is a reference clock signal;
Measuring a delay period between one end point of the calibration period and the particular characteristic of the observation target signal preceding the end point;
Starting a next calibration period such that its starting point is delayed in relation to the particular characteristic of the subsequent observation signal, the delay being equal to the measured delay period; Steps,
Arranging the calibration period in time by:
4. The method of claim 3, comprising measuring each delay period by counting characteristics of the reference clock signal.   The method according to claim 1, further comprising: obtaining a measured value of the frequency of the observation target signal by counting the characteristics of the observation target signal for each calibration period.   12. A method according to any one of the preceding claims, wherein the step of imparting an influence comprises setting a time reference utilized by the module.   The method according to claim 1, wherein the module is a real time clock unit.   A circuit configured to carry out the method according to claim 1.

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